OASIS Mailing List ArchivesView the OASIS mailing list archive below
or browse/search using MarkMail.

 


Help: OASIS Mailing Lists Help | MarkMail Help

 


 

   Re: [xml-dev] Making a silk purse out of the schema sows ear - was [xml-

[ Lists Home | Date Index | Thread Index ]

Well, looking at what you pointed to the first example also has
sorting, which is somewhat outside the bounds of what anyone has
discussed as validation before. As for the other ones I'm not exactly
sure what you're validating (maybe due to not having time to learn ASL
syntax)?

Actually this one
http://reflex.gforge.inria.fr/tutorial/weather-report/schema2.asl
looks like you're changing the value of the temp attributes if scale
attribute equals the Fahrenheit scale.

Another in the list of schema languages that people don't note too
often is DSD http://www.brics.dk/DSD/

Cheers,
Bryan Rasmussen



On 2/9/06, Philippe Poulard <Philippe.Poulard@sophia.inria.fr> wrote:
> This is a remark that has been made in comp.text.xml
>
> Unlike schematron, ASL computes content models, which allow
> tools such as editors to predict which element is allowed ; schematron
> is not predictive, it can only warn that a rule has not been followed
> AFTER the user has made the mistake, for example by inserting an element
> that is not allowed.
>
> There is a great difference between a tool such as schematron that
> checks if everything is right in the XML document, and other schema
> technologies (DTD, RelaxNG, WXS, ASL) that are able to draw up a
> contextual list of XML material (attributes, elements, text) that is
> legal to use. You can consider that the Active Schema Language is like a
> deep integration of known schemata (DTD, RNG, WXS) with an assertion
> language such as schematron ; a deep integration goes further than using
> schematron in WXS or RNG because even if they are located in the same
> XML instance, they are processed separately.
>
> Here is a mix of RNG + schematron :
> <?xml version="1.0" encoding="UTF-8"?>
> <grammar ns="" xmlns="http://relaxng.org/ns/structure/1.0";
>    xmlns:sch="http://www.ascc.net/xml/schematron";>
>    <start>
>      <element name="table">
>        <oneOrMore>
>          <element name="column">
>            <sch:pattern name="Check to have the same number of cells in
> each column" id="cells">
>              <sch:rule context="column">
>                <sch:assert test="count(../column[1]/cell) =
> count(cell)">The number of cells in this
>                  column should be the same as in the firtst column,
> expected <sch:value-of
>                    select="count(../column[1]/cell)"/> but got
> <sch:value-of select="count(cell)"/>.
>                </sch:assert>
>              </sch:rule>
>            </sch:pattern>
>            <oneOrMore>
>              <element name="cell">
>                <empty/>
>              </element>
>            </oneOrMore>
>          </element>
>        </oneOrMore>
>      </element>
>    </start>
> </grammar>
>
> Anyway, another point that is not covered by schematron is the
> capability to design smart data types such as semantic data types, as
> shown in this example :
> http://reflex.gforge.inria.fr/tutorial.html#N800F69
> This is a very basic problem that known schematas can't resolve.
> I think that neither WXS nor schematron could perform the same result
> (just tell me how if I'm wrong)
>
> bryan rasmussen wrote:
> > In Schematron - however going for xslt implementation of schematron by
> > using the current function:
> >
> > <sch:rule context="table/column[1]">
> >     <sch:report
> > test="following-sibling::column[count(cell)&gt;current()[count(cell)]]"
> >     >cells need to be the same number per column
> > </sch:report>
> >
> > </sch:rule>
> >
> > Cheers,
> > Bryan Rasmussen
> >
> >
> >
> >
> > On 2/9/06, Philippe Poulard <Philippe.Poulard@sophia.inria.fr> wrote:
> >
> >>hi,
> >>
> >>IMHO, the main difficulty that schema technologies encounter is their
> >>poor capabilities to express constraints because they are hard-coded in
> >>the schema. This is the case for occurrence constraints and content
> >>model definitions.
> >>
> >>I have experimented a schema language that allows to compute the
> >>occurrence constraints dynamically and that allows to switch from a
> >>declarative language to an imperative one, which increases dramatically
> >>the expressiveness of the schema. The idea is to push back the limits of
> >>the declarative language when they are reached.
> >>
> >>An example :
> >>a RelaxNG user was complaining about a constraint that he couldn't
> >>express : he had to design a <table> with any <column>s but <column>s
> >>should have the same number of <cell>s
> >>
> >>I respond that he could consider an alternative schema technology, such
> >>as these that I designed :
> >><asl:element name="column">
> >>   <asl:sequence>
> >>     <xcl:if test="{ asl:element()/preceding-sibling::column }">
> >>       <xcl:then>
> >>         <asl:element ref-elem="cell" min-occurs="{
> >>  $asl:max-occurs }" max-occurs="{ count( asl:element()/../column[1]/cell
> >>  ) }"/>
> >>       </xcl:then>
> >>       <xcl:else>
> >>         <asl:element ref-elem="cell" min-occurs="1"
> >>  max-occurs="unbounded"/>
> >>       </xcl:else>
> >>     </xcl:if>
> >>   </asl:sequence>
> >></asl:element>
> >>The full schema and the running results are available here :
> >>http://groups.google.com/group/comp.text.xml/browse_thread/thread/d97cd4adf1964fdb/2f92e65b7ad48dff?hl=en#2f92e65b7ad48dff
> >>
> >>This demonstrates that a simple if-then-else statement allows to build a
> >>made-to-measure content model with dynamic occurrence constraints.
> >>
> >>I named that schema language the Active Schema Language and I have an
> >>almost full implementation of it in Java, called RefleX :
> >>http://disc.inria.fr/perso/philippe.poulard/xml/active-tags/active-schema/active-schema.html
> >>http://reflex.gforge.inria.fr/
> >>You can read the examples, download the tool and play with it.
> >>
> >>Moreover, ASL allows to design smart data types ; there is a tutorial in
> >>the RefleX web site that shows a semantic data type : the "temperature"
> >>data type, which is able to parse "32F" and "20C" ; as this type is
> >>used to augment the amount of information of the XML document, we can
> >>sort a list of attributes of this type not on the string values but on
> >>the typed values
> >>http://reflex.gforge.inria.fr/tutorial.html#N800F69
> >>
> >>It is worth seeing because all the problems you consider in your message
> >>are pointed out and solutioned in ASL.
> >>
> >>Michael Champion wrote:
> >>
> >>>I think the reality is that lots of people flipped the Bozo Bit on the
> >>>XSD spec in 1999-2000.  They went in different directions, however:
> >>>Some to alternative schema languages, some to radical simplification of
> >>>XML to de-emphasize schemas altogether.
> >>>
> >>>
> >>>
> >>>In hindsight, had  people foreseen today's reality that we're stuck with
> >>>XSD as what the mainstream user thinks of as the "real standard",
> >>>clearly the energy would have been better spent debugging the wretched
> >>>thing rather than trying to pretend it doesn't exist or trying to drive
> >>>a stake thru its heart.  I'm more interested in discussing what to do
> >>>going forward given the current mess.  The problems I see are:
> >>>
> >>>
> >>>
> >>>- The W3C is more interested in moving the XSD spec forward than fixing
> >>>its numerous ambiguities.  (Their pushback is that the people who want
> >>>to fix it are not represented on the WG, and the people who have skin in
> >>>the game want to move forward).
> >>>
> >>>- RELAX NG is clearly "better" for textual documents but doesn't have
> >>>much support for the data-oriented use cases. (Sure you can plug in the
> >>>XSD type system, but that's a big part of the problem).  We now have an
> >>>unpleasant situation of fragmentation where there's little mainstream
> >>>tool support for RELAX NG due to lack of demand, exploitation of its
> >>>geek chic (partly to strike a blow against the empire, I suppose), with
> >>>the result that the normative definitions of Atom and ODF can't be used
> >>>with most commercial XML tools.  Maybe a good guerilla tactic in the
> >>>open source wars, but for the moment it's the innocent who suffer the
> >>>collateral damage.
> >>>
> >>>
> >>>
> >>>- Schematron is moving forward as an ISO standard and has some good
> >>>implementations but has few normative references in vertical industry
> >>>standards nor mindshare.  (Correct me if I'm wrong about the normative
> >>>references).
> >>>
> >>>
> >>>
> >>>- Lots of people complain about the limitations of XSD that Schematron
> >>>addresses and the W3C doesn't plan to, especially the lack of occurrence
> >>>constraints.
> >>>
> >>>The best way forward that I can see is to encourage end users to
> >>>employ XSD + Schematron as necessary, and encourage W3C to address XSD's
> >>> bugs and ambiguities before adding more onto an unstable foundation.
> >>>What does that miss that the world actually values? (as much as it
> >>>depresses me to say it, the world doesn't seem to value RELAX NG's
> >>>elegance and mathematical foundation very much).
> >>>
> >>
> >>--
> >>Cordialement,
> >>
> >>               ///
> >>              (. .)
> >>  --------ooO--(_)--Ooo--------
> >>|      Philippe Poulard       |
> >>  -----------------------------
> >>  http://reflex.gforge.inria.fr/
> >>        Have the RefleX !
> >>
> >>-----------------------------------------------------------------
> >>The xml-dev list is sponsored by XML.org <http://www.xml.org>, an
> >>initiative of OASIS <http://www.oasis-open.org>
> >>
> >>The list archives are at http://lists.xml.org/archives/xml-dev/
> >>
> >>To subscribe or unsubscribe from this list use the subscription
> >>manager: <http://www.oasis-open.org/mlmanage/index.php>
> >>
> >>
> >
> > -----------------------------------------------------------------
> > The xml-dev list is sponsored by XML.org <http://www.xml.org>, an
> > initiative of OASIS <http://www.oasis-open.org>
> >
> > The list archives are at http://lists.xml.org/archives/xml-dev/
> >
> > To subscribe or unsubscribe from this list use the subscription
> > manager: <http://www.oasis-open.org/mlmanage/index.php>
> >
> >
>
>
> --
> Cordialement,
>
>                ///
>               (. .)
>   --------ooO--(_)--Ooo--------
> |      Philippe Poulard       |
>   -----------------------------
>   http://reflex.gforge.inria.fr/
>         Have the RefleX !
>




 

News | XML in Industry | Calendar | XML Registry
Marketplace | Resources | MyXML.org | Sponsors | Privacy Statement

Copyright 2001 XML.org. This site is hosted by OASIS